An employee tasked with purchasing goods for a specific amount: is he permitted to buy them from another person at a lower price and keep the difference?

Question:
He says: Honorable Shaykh, may Allah grant you success, is it permissible for an employee who is tasked with purchasing an item for a company, such as a car, for a certain amount, to buy the car from someone he knows at a lower price? Is it permissible for him to take the difference from the seller by agreement with him, and write the original amount on the invoice along with the price difference?

Answer:
This is not permissible. This is lying and betrayal. He writes the actual price on the invoice, and does not lie and take the extra amount.